src/advent14/advent14.hs

   1 import Data.List.Split (chunksOf)
   2 import Data.Char (ord)
   3 import Text.Printf (printf)
   4 import Data.Bits (xor)
   5 import qualified Data.Map.Strict as M
   6 import qualified Data.Graph as G
   7 import Control.Parallel.Strategies (parMap, rpar)
   8 type CellMap = M.Map (Int, Int) Bool
   9
  10 puzzleKey = "xlqgujun"
  11
  12 main :: IO ()
  13 main = do
  14   print $ part1 puzzleKey
  15   print $ part2 puzzleKey
  16
  17
  18 part1 :: String -> Int
  19 part1 key = sum rowCounts
  20     where rowCounts = parMap rpar countSetBits $ binHashes key
  21
  22
  23 part2 :: String -> Int
  24 part2 key = length $ cellEdges cells
  25     where cells = presentCells $ binHashes key
  26
  27 binHashes :: String -> [String]
  28 binHashes key = parMap rpar binHash $ rowSpecs key
  29
  30
  31 binHash :: String -> String
  32 binHash = binify . knotHash
  33
  34 numKey :: (Int, Int) -> Int
  35 numKey (r, c) = 128 * r + c
  36
  37
  38 presentCells :: [String] -> CellMap
  39 presentCells bhs = M.fromList [((r, c), True) | r <- [0..127], c <- [0..127], (bhs!!r)!!c == '1']
  40
  41 adjacentCells :: CellMap -> (Int, Int) -> [(Int, Int)]
  42 adjacentCells cells (r, c) = filter (\k -> M.member k cells) possibles
  43   where possibles = [(r, c - 1), (r, c + 1), (r - 1, c), (r + 1, c)]
  44
  45
  46 cellEdges :: CellMap -> [G.SCC (Int, Int)]
  47 cellEdges cells = G.stronglyConnComp [(k, numKey k, map numKey $ adjacentCells cells k) | k <- M.keys cells]
  48
  49 rowSpecs :: String -> [String]
  50 rowSpecs key = map (((key ++ "-") ++) . show) ([0..127] :: [Integer])
  51
  52 countSetBits :: String -> Int
  53 countSetBits = length . filter (== '1')
  54
  55
  56
  57 knotHash :: String -> [Int]
  58 knotHash input = densify tied
  59     where (tied, _, _) = foldl step ([0..255], 0, 0) hashTerms
  60           hashTerms = mkHashTerms input
  61
  62 step :: ([Int], Int, Int) -> Int -> ([Int], Int, Int)
  63 step (original, start, skip) len = (replaced, start', skip + 1)
  64     where replaced = tie original start len
  65           start' = (start + len + skip) `mod` (length original)
  66
  67 tie :: [a] -> Int -> Int -> [a]
  68 tie original start len = replace original replacement start
  69     where replacement = reverse $ extract original start len
  70
  71 extract :: [a] -> Int -> Int -> [a]
  72 extract items from len = take len $ drop from $ items ++ items
  73
  74 replace :: [a] -> [a] -> Int -> [a]
  75 replace original replacement from = take (length original) (start ++ replacement ++ remainder)
  76     where excess = drop (length original - from) replacement
  77           stub = drop (length excess) original
  78           start = take from (excess ++ stub)
  79           remainder = drop (length $ start ++ replacement) original
  80
  81
  82 mkHashTerms :: String -> [Int]
  83 mkHashTerms text = take (length chunk * 64) $ cycle chunk
  84     where chunk = map ord text ++ [17, 31, 73, 47, 23]
  85
  86 -- hexify :: [Int] -> String
  87 -- hexify = concatMap (printf "%02x")
  88
  89 binify :: [Int] -> String
  90 binify = concatMap (printf "%08b")
  91
  92 densify :: [Int] -> [Int]
  93 densify ns = codes
  94     where chunks = chunksOf 16 ns
  95           compress = foldl1 xor
  96           codes = map compress chunks